During intermediate vehicle stops such as at a traffic light, an engine may idle for some time. In order to increase fuel efficiency and improve emissions quality, the vehicle engine may be equipped with a start-stop function to reduce prolonged idling by temporarily shutting down the engine and then restarting the engine when restart conditions are met. Entry conditions for engine idle-stops may be determined based on current vehicle and engine operating conditions.
Various approaches are provided for scheduling an engine idle-stop. In one example, as shown in U.S. Pat. No. 9,440,654, Atluri et al. teaches a method to determine entry and exit conditions for engine idle-stops based on short-term and long-term look ahead data obtained from on-board vehicle sensors and external sources such as a network cloud. Short-term and long-term look ahead data indicate conditions likely to occur in the future, with long-term look ahead vehicle operating conditions being further in the future than short-term look ahead vehicle operating conditions.
However, the inventors herein have recognized potential issues with such systems. As one example, even though scheduling engine idle-stops may be beneficial for fuel efficiency and emissions quality, engine idle-stops for shorter durations may adversely affect engine performance and fuel efficiency. Repeated engine idle-stops that are shorter than a threshold duration may cause degradation of engine components. During engine restart immediately following an idle-stop for a shorter than threshold duration, a higher amount of energy may be used during engine cranking relative to the amount of energy saved by reducing fuel consumption, thereby affecting overall fuel efficiency. Also, frequent engine idle-stops may cause a series of perceivable changes in engine sound which may be objectionable to a vehicle operator.
In one example, the issues described above may be addressed by a method comprising: receiving data indicative of external vehicle conditions to a vehicle including a length of a line of vehicles and relative movement within the line, adjusting vehicle operating thresholds responsive to the data, and selectively activating or deactivating an engine responsive to the thresholds and the data. In this way, by adjusting vehicle operating thresholds for engine idle-stop based on upcoming traffic and road information as received from remote sources, engine idle-stops for a shorter than threshold duration may be reduced.
As one example, traffic information including length of a line of vehicles stopping in a road ahead of the vehicle and relative motion between individual vehicles in the line of vehicles may be obtained from remote sources. The on-board controller of the vehicle may be communicatively coupled to on-board controllers of one or more vehicles in the line of vehicles, such as using vehicle to vehicle (V2V) communication technology. The controller on-board the vehicle may also be wirelessly coupled to external networks and/or traffic sensors, such as using vehicle to infrastructure (V2I) communication technology. The on-board controller may retrieve upcoming traffic information including vehicle speed, a nature of relative movement of the line of vehicles, and acceleration profiles of each vehicle in the line of vehicles from the aforementioned remote sources. The on-board controller may also retrieve road segment characteristics data including gradient and curvature of road immediately ahead of the vehicle from the remote sources. A duration of engine shut-down of the vehicle during an upcoming possible engine idle-stop may be estimated based on the retrieved traffic information and road segment characteristics. In one example, if it is determined that the duration of engine shut-down is longer than a threshold duration, engine idle-stop may be initiated by suspending fueling to the engine cylinders. The threshold engine shut-down duration may be estimated based on fuel efficiency gained from the engine shut-down and electric motor power consumption for engine cranking during an engine start immediately following the shut-down. In another example, if it is determined that the duration of engine shut-down is longer than a threshold duration, one or more vehicle operating thresholds including a state of charge of an electric motor battery threshold and an electrical accessory load threshold may be modified to expedite engine shut down responsive to the idle-stop conditions being met. If it is determined that the duration of engine shut-down is shorter than a threshold duration, the engine may not be idle-stopped even if other idle-stop conditions are met. Upcoming periods of increased engine load may be estimated based on the retrieved traffic information and road segment characteristics. Regeneration of an exhaust particulate filter may be opportunistically scheduled during such periods of increased engine load.
In this way, by estimating the duration of engine shut-down of the vehicle during an upcoming possible engine idle-stop and idle-stopping the engine responsive to a longer than threshold estimated duration of the possible idle-stop, frequent engine idle-stops for shorter than threshold durations may be reduced. By estimating the threshold duration of the engine shut-down during a possible idle-stop based on fuel efficiency gained from the engine shut-down and electric motor power consumption for engine cranking during an immediate engine start following the shut-down, fuel efficiency benefits may be increased while reducing loss of battery power due to frequent operation of the starter motor. The technical effect of using traffic data including length of a line of vehicles ahead of the vehicle and relative movement within the line as available from external sources is that the estimation of the duration of engine shut-down of the vehicle during an upcoming possible engine idle-stop may be made with higher accuracy. By reducing repeated engine idle-stops for shorter than threshold durations, degradation of engine components may be lowered and perceivable changes to engine sound due to the frequent engine idle-stops may be reduced, thereby increasing overall operator satisfaction.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.